I think that the Soviet Union may have incentive to cooperate with regard to global warming since global warming is transcontinental and may result in the end of civilization if allowed to continue. According to National Geographic video a temperature increase of five degrees can cause the collapse of civilization. At the present time Siberia is cold and is generally unsuitable for agriculture. If it warmed up then the Soviet Union may be willing to allow immigration to the north in order to help populate Siberia.